u-blox SARA-R520 Smart Connection Manager User Guide

u-blox SARA-R520 Smart Connection Manager

Product Specifications

• Product Name: LEXI-R520 / SARA-R52 series
• Feature: Smart Connection Manager (uSCM)
• Document Number: UBX-21006919
• Revision Date: 12-Apr-2024
• Supported Products: LEXI-R520, SARA-R520, SARA-R520M10

Product Information

The u-blox Smart Connection Manager (uSCM) is a feature that maintains and automatically reestablishes the network registration and data connection in case of unexpected out-of-coverage conditions or any other interruption in the communication link.
Once enabled, uSCM handles all connectivity aspects, covering corner cases that are difficult to manage. It continuously monitors the network status, tracks user activity, and follows the profile configuration stored in a configuration JSON file in the module filesystem (FS).

Product Usage Instructions

Smart Connection Manager Overview
The uSCM manages network registration and data connection reestablishment automatically.

To enable uSCM:

1. Ensure the module filesystem (FS) contains the configuration JSON file.
2. Monitor network status and user activity.
3. Follow profile configurations for seamless operation.

AT Commands
The product supports AT commands for configuration.

To use AT commands:

1. Refer to the product manual for a list of available AT commands.
2. Send AT commands to configure uSCM settings as needed.

Use Cases
The uSCM can be used in various scenarios to maintain network connectivity.

Some common use cases include:

• Handling out-of-coverage situations.
• Reestablishing data connections after interruptions.
• Managing network registration seamlessly.

Frequently Asked Questions (FAQ)

1. Q: How do I know if uSCM is enabled?
   A: Check the module filesystem for the presence of the configuration JSON file. If it is stored, uSCM is likely enabled.

2. Q: Can uSCM handle all network-related issues automatically?
   A: uSCM aims to cover most connectivity aspects automatically, but some complex issues may require manual intervention.

Abstract
This application note describes the functionalities of the u-blox Smart Connection Manager feature.

Document information

Title| LEXI-R520 / SARA-R52 series|
---|---|---
Subtitle| Smart connection manager (uSCM)|
Document type| Application note|
Document number| UBX-21006919|
Revision and date| R01| 12-Apr-2024
Disclosure restriction| C1-Public|

This document applies to the following products:

• Product name
• LEXI-R520
• SARA-R520
• SARA-R520M10

u-blox or third parties may hold intellectual property rights in the products, names, logos and designs included in this document. Copying, reproduction, modification or disclosure to third parties of this document or any part thereof is only permitted with the express written permission of u-blox.
The information contained herein is provided “as is” and u-blox assumes no liability for its use. No warranty, either express or implied, is given, including but not limited to, with respect to the accuracy, correctness, reliability and fitness for a particular purpose of the information. This document may be revised by u-blox at any time without notice. For the most recent documents, visit www.u-blox.com.
Copyright © u-blox AG.

Smart connection manager overview

The u-blox Smart Connection Manager (uSCM) is a feature that maintains and automatically re-establishes the network registration and data connection in case of unexpected out-of-coverage condition or any other interruption in the communication link.
Once enabled, uSCM handles all the connectivity aspects, automatically covering all the corner cases that are difficult to handle.
uSCM operates by continuously monitoring the network status and by keeping track of the user activity and profile configuration. All its functionalities are guided through the uSCM algorithm which operates following the profile configuration and settings reported in a configuration JSON file, if stored in the module filesystem (FS).
Some existing functionalities of the radio policy manager entity have been incorporated into the uSCM feature. In addition, the uSCM has implemented new processes, algorithms, and controls, as described in the following sections.

Features overview
Smart connection manager supports several features, and it provides a globally optimized connectivity with automatic APN detection and handling. Additionally, through proper configuration, all the network settings (e.g., QoS and MNO optimize selection) are managed by uSCM. Furthermore, it facilitates low-power designs by implementing protection mechanisms to avoid ping-pong among cells and minimize the cell scan time. .

Additional features included are:

• SIM initialization.
• Possibility to handle multiple contexts with different configuration values.
• Transmission/networking/policies optimizations.
• Behavior monitoring and patterns identification.
• Detect out-of-coverage (OOC) situations. By OOC condition, the document is referring to any unsuitable conditions of the module where it cannot attempt the registration and/or if attempted this would fail.
• Possibility to automatically handle the APN selection
• Able to operate in a low-power scenario where the PSM is adopted.
• Data stall detection
• Cell ping-pong detection and relaxed cell monitoring
• Network connection KPI monitoring (SR failures, connection reestablishment count, RACH failures)
• Enhanced configuration for low power scenarios with static conditions.

The uSCM algorithm integrates all these features with the help of several working states, which are described in the next section.

Working states

• uSCM initialization: uSCM is enabled via the +USCM AT command. Once enabled, it moves from the HALT state to the INITIALIZATION state. The initialization phase consists of some preliminary checks such as antenna presence and module ambiance temperature. If already registered to the network, the module will be deregistered so that uSCM performs all the start-up steps with full control of the registration process. All the RAT and CS/PS profile settings are read and taken from the module AT settings.
• Connection Establishment: After completing the initialization, uSCM moves to the CONNECTION_ESTABLISHMENT state. This state enables the module cellular functionalities and monitors the registration status. Once registered, also the packet switch data profile and PDP contexts are activated if properly configured in the parameters of the configuration file. As the final action in this step, uSCM either moves to the CONNECTION_MAINTENANCE state if registration and context activation is successful or it triggers a RECOVERY procedure if a failure is observed.
  • Context activation: uSCM will ensure that all the PDP context defined in the configuration file are activated. In particular:
• In HPLMN: all the CIDs present in configuration files, marked for “home”, will be activated. Failure in any CID will result in an error.
• In VPLMN: all the CIDs present in configuration files, marked for “roaming”, will be attempted for activation. No error will be returned if at least one CID is activated.
  • Registration status monitoring: This state helps uSCM to determine if the module is in a correct registration state with respect to CREG/CGREG/CEREG status, RAT setting, and CS/PS profile settings.
• Connection maintenance: In connection maintenance, uSCM will observe the registration status and others network KPIs which can indicate the health of connection. uSCM keeps the track of Cell IDs and Tracking Area Codes (TAC), any ping-pong in same Cell IDs or TACs may trigger the recovery response. If there is a failure in registration status due to out-of-coverage or weak coverage, RECOVERY is triggered.
• • Recovery: uSCM will enter the recovery process if out-of-coverage or weak coverage conditions occur. Moreover, also the identification of a context activation failure brings uSCM to this recovery state. A complete list of all the possible recovery causes can be found in the description of +UUSCMSTAT URC message in the AT commands manual [5].
  • Coverage failure: When the module is not registered for an amount of time, coverage failure will be detected by uSCM.

uSCM timers
Several timers are maintained and monitored in the uSCM feature. These timers are used to monitor the different transit conditions and act accordingly with the uSCM functionalities.

• Scan Timer: Triggered immediately when the module is de-registered, (reported by +CEREG: 4 URC) the module is allowed to scan the PLMN for this time as per the default platform scheme. If the timer expires the module will enter the to save power. uSCM will maintain the module in this last mode for an interval of time defined by the backoff timer.
• Weak Coverage Interval Timer: Determines the maximum time interval (in seconds) during which the change between normal service and limited service/out-of-coverage condition is considered an unexpected event and is used to increment the guard counter. When the guard counter reaches the , the module enters to save power as after the scan timer.
• Backoff Timer: When uSCM determines that the module is in out-of-coverage conditions (i.e., RSRP is in-valid and the scan timer expiries), it will take the module into (Radio Switch off Mode or Low Power Mode can be selected by editing parameter in the configuration file) for backoff timer. This will help the module to save power during OOC conditions. This backoff timer defines the amount of time that the device will stop scanning for network and will remain in . Once uSCM moves to the CONNECTION_MAINTENANCE state, the PSD timer is reset to its initial value, set in .

Configuration file
uSCM operates based on the functional configurations.

You have two options to specify the configurations:

• Use the pre-defined functional configurations profiles available in uSCM. Users can select any of the four configuration profiles by the +USCMCONF AT command.
• Use a functional configuration file (which is a single JSON file) to configure its functionalities if settings differ from the default profile values.

This section explains how to get access, edit, and update the functional configuration file. See example of the configuration file in appendix C.
The following sections provide instructions on how to deploy the configuration JSON file to the module and how to modify it.

Store functional configuration file with AT commands
The configuration file can be transferred to the module file system (FS) with the following AT commands.

scm_config.json file to the module FS. : is the data count of file content to be
Command| Response| Description
---|---|---
| | transferred. ‘SCM’ is used as Tag for selecting the specific folder to store the file.
AT+ULSTFILE=0,”SCM”| +ULSTFILE: “scm_config.json” OK| Verify if the configuration file is present in the module FS.

Any firmware update (either FOTA, FOAT, or via Easyflash) will remove the user configuration files from the module filesystem. Therefore, we recommend performing a backup of the configuration files, so they can be reloaded after the firmware update.

Store functional configuration file with m-center
You can use m-center evaluation software to store the JSON file into the module.
In the ‘Tag’ field it is mandatory to report the ‘SCM’ parameter to store the configuration file in the correct folder.
Any file can be stored in the module via the File System Tab shown in Figure 1, by clicking Store file. A window will open where the chosen file can be selected from Windows Explorer.
By clicking Dir, the m-center window will display all the stored files.
Download the latest version of m-center for free at https://www.u-blox.com/en/product/m-center

Figure 1: m-center File System tab
Modify functional configuration file
All the parameters in the JSON file are categorized by their characteristics and defined with multiple sub-objects. The configuration manager in uSCM is responsible for loading the functional configurations.
See appendix A for descriptions and ranges for all configuration settings.
The use of the configuration file is not mandatory. In case a specific setting, different from the default profile, needs to be used, the user can download the configuration file and store it on the module. By properly defining a new value for this specific setting, uSCM will parse the content of the configuration file and overwrite the default profile value.
☞ Not all the settings must be reported in the JSON file, only the ones that differs can be reported.
☞ If the user loads configurations through the JSON file, the configuration manager will parse the configuration file stored in the FS. It checks for any out-of-range parameter, and if the file is correct, loads the configuration file in uSCM.

Initialization configurations
Update the following JSON object in the configuration file to define the module temperature ranges.
“init_info”:
{
“reg_profile”: 4
}

PDP context list
All the PDP contexts to be activated must be listed in the functional configuration file. Update the following JSON object to add any PDP context.
“ctxt_act”:
{
“cid_count”: 3,
“ctxt_data”:[[0,0,”APN1″],[2,0,”APN2″],[5,1,”APN3″]] }

Power saving mode configuration
Update the following JSON object in the configuration file to define the parameters of the power saving mode configurations.
“power_saving_mode”:
{
“suspend_mode”: 1
}

AT commands

This section reports all the AT commands that are related to the uSCM functionalities. For details of the AT commands, see the AT commands manual [2].

uSCM control (+USCM)
The +USCM AT command provides the entire uSCM top level control. It enables or disables the uSCM feature and URCs.
The uSCM feature is disabled by default.
All the uSCM URC notifications can be identified with the string +UUSCMSTAT.

uSCM configuration (+USCMCONF)
The +USCMCONF AT command selects, reads, or resets (to the factory-programmed values) the uSCM profile parameters with the. It allows the user application to switch the functional default profile at run time even if uSCM is already enabled.
If an invalid configuration filename is provided, the +USCMCONF command will return an error and uSCM will start with the default profile.
The command can select between uSCM functional configurations from user configuration or the default profiles. The default profiles are shipped with different values of configuration parameters as per the profile requirements.
Along with this +USCMCONF AT command, uSCM low level configurations are managed by a JSON formatted configuration file. This configuration file shall be stored in the module filesystem. See section 1.3 for details of configuration transfer and modification.

URC notifications
The URC +UUSCMSTAT reports changes in the uSCM state but also any other error and/or warning. Precisely, accordingly with its structure +UUSCMSTAT: ,[,[,]], the first argument is used to indicate the type of reported URC which may vary in three different categories. Those categories are all highlighting a change in the uSCM state. However, the change may occur normally, with a warning and with an error condition.
For a complete list of all the possible values arguments and the different <param#> may assume, see the AT commands manual document [5].